Moistureproof cellulose acetate sheeting



Nov.-5, 1935. N. F. BEACH ET AL 2,019,648

MOISTUREPROOF CELLULOSE ACETATE SHEETING Filed July 17, 1931 Gum 5Fig.2.

June 450m 1Z0rmaIpEBeach& James m1,

Patented Nov. 5, 1935 I Norman F.

Beach and James G. McNally,

Rochester, N. Y.,.assignors to Eastman Kodak Company, Rochester, N. Y.-,

New York a corporation of Application July 11, 1931,, Serial No. 551,490

is. Claims. (01. 91410) This invention relates the manufacture of thincellulosic acetate sheeting andmore particularly to a waterproof andmoistureproof sheet- 7 ing having superimposed thereon separate layersof gum and wax.

It is known to coat paper, cloth, and other forms of cellulosic materialwith waxes or gumsfor the purpose of rendering them impenetrable orimpermeable to water and other liquids. So

far as we are aware, however, there has been no attempt to waterproof ormoistureproof cellulose acetate sheeting by the method hereinaiterdescribed. The present invention is not concerned broadly with eitherwaterproofing or moisture-' proofing, but relates to the treatment of acolloidized' cellulosic base sheet and involves the use of a type ofcoating material which, due to its peculiar properties, requires aspecial technique. The resulting moistureprooi coating not onlydiiiersfrom known coatings in the requirements with respect to its mode ofapplication,

but also diiiers in composition in that it contains only two necessaryingredients and does not require the presence of a base material such ascellulose nitrate, cellulose acetate or other cellulose esters orethers.

Thin cellulose acetate sheeting has found wide use as wrapping orpackaging material, due to the fact that it is comparatively tou h,flexible,

transparent, and impermeable to dust and similar foreign .matter. Itsprincipal drawback for this purpose is that, as ordinarily produced, itis not waterprooi or moistureprooi, and, for this reason cannot be usedfor wrapping products where substantially-complete exclusion of moistureis important. For example, untreated cellulose acetate sheeting of theorder of .001" in thickness will transmit as much as 1.0 to 1.5milligrams oi water vapor per sq. cm. per hour. The improved productwhich is the subject of the present invention, however, will in somecases transmit as little as .002 milligrams of water under the sameconditions, thus showing a marked improvement in water-resistantproperties overuntreated' sheeting.

The principal object of our invention is to produce a highly waterproofand moistureproot formof thin cellulose acetate -sheetiitig. A furtherobject is to provide a wrapping or packaging material which is not onlyhighlywater-resistant but is also transparent, flexible, odorless, andnon-tacky. Another object is to provide a simple but effective methodfor moistureproofing thin cellulose acetate sheeting, while at the sametime preserving its flexibility, transparency, and

' sides of the sheet.

ins for forming the gum coating,

other essential and valuable properties. Other objects will appearhereinafter.

These objects are accomplished by the following invention which in itsbroadest aspect may be said to comprise applying to a thin basesheet 5-of cellulose acetate a first coating of a gum or resin and then applyinga second coating of wax'. These materials are preferably applied in theform of solutions in suitable solvents or they may be applied in amolten state, in separate 10 layers, the gum or resin layer in eithercase being applied first to'form a strongly adhering coat followed bythe wax coating which, in turn, is

strongly held by the gum or resin coat. The sheet may be coated onone orboth sides. In 15 case it is to be coated on two sides, this may beaccomplished in successive operations, or both sides may be coatedsimultaneously with a given solution, as will more fully appear in thefollowing description in which reference is made to 20 the drawingforming a part 0! this application.

In thedrawing,

Figure 1 is a diagrammatic representation oi I one form of apparatus forcarrying out the in vention, in which the sheet is coated on one sidewith successive layers of coating mate 1 I Figure '2 is a diagrammaticrepresentation oi apparatus similar to, and for use in connection with,that of Figure 1 when it is desired to coat 7 both sides oi the sheet.

Figure 3 is also a diagrammatic representation oi thev equipment forsimultaneously coating both variety of game or res= typical examples ofthese materials being ester gum, dammar, rosin, and sandarak. Natural orsynthetiegums or resins are eqhally desirable for this purpose. Any ofthese gums or resins may-beused alone or in combination with one anotheror with many 40 other gums or resins of this general nature which areiznown to those skilled in the art. The gun must, of course, adhere wellto the base sheet and must hold the wax coating without separation.

The wax coating. may consist of ceresin, beeswax, pimela, lanolin,Montan, bayberry, halowax, japan, oandelilla, Chinese wax and othersimilar waxes, any of which may, as in thecase of the gums, be used .50separately or in co 'bination with one another.

Our invention is distinguished by the application of two or more layersof waterproofing material, the first of which is a gum or resin. whichadheres closely to the base sheet by virtue We may employ a large of itsadhesiveness with respect to cellulose ace-' chloride, ethylenedichloride, and trichiorethyl-- ene, or similar solvents, it only beingnecessary in choosing the solvents to select one which is a good solventfor the gum, but substantially a non-solvent for cellulose acetate. .Aliquid possessing any appreciable solvent power for cellulose acetatewould not be desirable, since it would have a tendency to dissolve andweaken the base :0 sheet during coating and thereby render it unfit foruse.

With regard to wax solvents, it may be said that the hydrocarbons suchas gasoline, kerosene, petroleum ether, and other compounds of thisgeneral nature are preferable. Inasmuch as the wax coating issuperimposed on the gum or resin coating, the same care in the selectionof the solvent is unnecessary, since the first ad-' hesive coating ofgum protects the cellulose acetate sheet to a certain extent from theaction of the solvent which may be used in the wax solution. It isnecessary, however, to selecta solvent which has no pronounced solventaction on the gum, as otherwise the gum coating would be dissolved fromthe base sheet. As indicated above, the gum and wax need not necessarilybe put into solution, although from the standpoint of convenience inhandling they can be more readily and conveniently epplied in this way.If desired, each of these materials may be liquefied and app d in amolten condition. In some cases it may be an 'advantage to carry out theoperation in this way, since less complicated drying apparatus isrequired and the drying time may be somewhat shorter. The properties ofthe finished product, such as waterproofness, moistureproofness,flexibility, and transparency, may be controlled within certain limitsin accordance with the particular qualities desired, by varying theamounts of gum and wax making up the composite coating. With regard'tothe waterproofing properties of the coating, it may be stated that, ingeneral, the higher the proportion of wax to gum or resin,

the greater will be the water resistant properties, although it isnecessary to control the amount of wax in such a way that thetransparency of the original acetate sheet is not adversely affected. Wehave found that if too so thick a coating of wax is applied, thematerial will have a tendency to feel greasy and show finger marksreadily. On the other hand, if the proportion of gum is too high, thematerial will be objectionably tacky. It should be under- 5 stood,however, that as a general rule the more resinous material present, the'better will be the' adhesion properties of the composite coating.

' In the following examples we have set forth examples of a typical gum,a typical wax solu- 7 tion, anda typical combination gum-wax solution,respectively, but it is to be understood that these formulae are merelyillustrative and are not intended as a l mitation of our invention,

since it will be obvious to those skilled in the 75 art that a largervariety of similar compositions of solvent vapors.

sheet I passes to wind up roll I3.

may be made up in accordance with the present description.

Example of typical gum-containing solution Percent by weight 5 Ester gum80% toluene {20% ethylene dichloride} Example of typical was: solution10 Percent Paraiiin wax 1 Petroleum distillate boiling between C.

and 70 C. 99

Example of typical gum wax solution 15 Percent Paraffin 3 parts 1 Estergum 1 part Ethylene dichloride 15 20 Toluene 84 a drying chamber whichis preferably provided with suitable means (also not shown) formaintaining the desired temperature and for removal The numeral 1indicates a 35 second subbing roll having positioned thereover andcooperating therewith squeeze roll 8. Roll I is normally partiallyimmersed in a second bath of coating soution 9 contained in vat I0,which, as in the previous case may be provided with known means formaintaining the coating material in a fluid condition. Numeral IIdesignates a drying chamber similar to chamber 6. Numeral I2 is a guideroll over which the Figure 2 shows additional apparatus for use inconnection with the equipment shown in Figure 1, I 4 being a guide rollover which the sheet I passes to a subbing roll I5 having positionedthereover and cooperating therewith squeeze roll IS, the function ofrolls I5 and I6, as well as I9 and 20, being the same as rolls 3 and 4,and I and 8, respectively, of Figure l. The vats I8 and 22 also serve apurpose similar to that of 5 and 10. In like manner, drying chambers 23and 24 55 operate in a manner similar to drying chambers 6 and II.Numeral 25 designates a guide roll over which the finished sheet passesto windup roll 26.

Figure 3 shows an optional form of equipment 60 for simultaneouslycoating both sides of a base sheet with a series of waterproofingmaterials according to the invention. Numeral 21 designates asupply rollfrom which the base sheet I is passed over guide roll 28. Numeral 29represents an immersion roll normally partially immersed in coatingfluid 30 contained in vat I I Numerals 22 and 32 designate aconventional form of scraping device for removing excess coating fiuidfrom the sheet and insuring uniform application. 7

Numeral 34 is a guide roll over which the sheet I a similar manner bymeans of rolls 1 and 8, dried up the gum coating fluid I and carryingit. onto the under surface of the base sheet. Roll 0 squeezes oil theexcess fluid which eventually returns to the bath. The sheet then passesthrough the drying chamber 6 where the material applied is merely driedat the proper temperature. The second layer of wax is applied from bathI in in drying chamber ll, passed over guide roll l2,

and finally wound up on roll II; If it is desired to coat both sides ofthe sheet, instead of being wound up on roll l3, the sheet may be passedaround another guide roll ll, thence first through a gum coatingoperation between rolls l5 and I6, then through a wax coating operationbetween rolls l9 and 20; and finally wound 'up upon roll 26,

drying of the sheet being accomplished by passage through dryingchambers 23 and 24 as in the case of the single coating process ofFigure 1.

If it is desired to apply a gain coating to both sides of the sheetsimultaneously, the apparatus of Figure 3 may be employed. In this casethe sheet I, fed from supply roll 21, passes over guide roll 28,immersion roll 29, between scrapers 32 and 33, over guide roll 34 andthence to drying chamber 35. During the passage of the sheet over roll29, the vat Si is raised to the proper height which,

places the roll well beneath the surface of the fluid 30 with the resultthat the coating liquid flows freely into the opening between thedowncoming and up-going portions of the sheet, thereby insuringapplication of the material to both sides thereof at the same time.Excess fluid is removed by scraper bars 32 and 33 which also assist inan even distribution of the material over the surface of the sheet. Thesingle-coated sheet is then dried at the proper temperature by passingthrough drying chamber and is then subjected to a coating of wax bypassage t ugh bath 39, roll 31 and dryingchamber ll perform ing the samefunctions as previously described, a d the finished sheet is finallywound up on roll It is to be understood that the apparatus hereindescribed is intended to be merely illustrative and that many changesmaybe made therein without in any way departing from the scope of ourinvention. It is conceivable that other t s of apparatus might be usedwith equally desirable results in carrying out our process. In fact,

the particular apparatus shown and described herein does not of itselfform any part of the invention and is intended to be merely conven-'-tional.

As illustrating the highly desirable results to be obtained by the useoi' our process, the following typical examples of coating operationsare given below. a Example i v,

A gum solution consisting of ester gum in toluene was applied byhnersion to a'base sheet of cellulose acetate of about .001" thicknesshav- 'ing an original capacity for transfusion of of 1.01to 1.5milligrams per square centimeter per hour. lifter drying at atemperature of 50-105.

tive seal therebetwcen may the points. of contact.

0., a second of solution consisting of 54% ofa 139 paramn,dissolved in acommercial hexane having a boiling point of 60 to 70 C. was thereafterapplied in the same mann'e the sheet be- I ing dried at 50 to 105 C. Thecoated sheet was 5 found to transmit only .005 milligrams per squarecentimeter per hour.

Example I! A solution containing 1% ester gum dissolved in toluene wasapplied by a subbing operation to a cellulose acetate base sheet similarto that used in Example 1. After drying at a temperature of 50 to 105 C.a second solution containing 3% candelilla wax dissolved in gasoline wasapplied in the same manner as'the gum solution and dried at the sametemperature as before. The sheet was found to transmit only .026milligrams of water per square centimeter per hour.

Example III Y 50 0.,the sheet was coated with a second solutionconsisting of 5% of a 139 paraiiin dissolved in a a commercial hexanehaving a boiling point of 80 to 70 C. Afterdrying, the double coatedsheet was found to transmit only .004- milligrams of water persquare-centimeter per hour.

It is a feature of our invention that the double coating of the sheet asit emerges from the bath of wax solution may, if desired-be subjected toa temperature during the last drying operation sufficient to cause thegum and wax layers tounitc or coalesce at their mutual boundary with theresult that the coating will range all the way from 100% wax at theoutside to 100% gum at the portion in contact with the base sheet.

The-double coated product of our invention is readily susceptible toheat or solvent sealing. For example, when two sheetsare brought toether with their coated-surfaces in contact, an eifec- I be made merelyby the application of heat and pressure, the respec: tivemoistureproofcoatings readily softenin and flowing together, to form a satisfactoryjoint at The application of pressure will enhance the coalescing eifectproducm by the heat and serve to ring the sheets into even closerrelation and cause them to adhere strongly to'one'another. J

Whilewe prefer to use a base sheet having -a thickness of the order of.001", it is entirely to the purpose of our invention, are plasticiserssuch as tricresyl phosphate, triphenyl phosphate,

benzyi benmate, and other plasticizing or softeningagents. Furthermore,various spirit.- and oil- 0 soluble dyes, aluminum flake, gold leaf,pearl. essence, and other coloring materials may be included in thecomposition, or may be incorporated directly-into the original esterdope from which the base sheet'is produced. Perfumes or flavoring 7whichthe finished product is ultimately to be put.

- Likewise various ultra-violet filters, such, for example, as thosedescribed in the co-pending application of Richardson and Stan SerialNo. 457,508, filed May 29, 1930, may be advantageously used in themanufacture of moistureproof sheeting which is to be used for thewrapping of delicately tinted articles which have been dyed with dyeswhich are fugitive to ultra-violet light.

It has also been found that the waterproof sheeting of our invention isreadily susceptible of being united or joined by applying varioussolvents to the portions of the material it is desired to unite andbringing them into close contact. As in the case of simple heat sealing,suchasdescribed above, heat and pressure are advantageously used tocause those portions of the moistureproof sur- 1:

face which have been softened or partially dissolved by the solvents tocoalesce and, upon evaporation of the solvent, to form a strong,uniform, and transparent joint or seal. The heat evaporates oi! thesolvent and leaves only the mingled or coalesced portion of the coatingsof the respective sheets adhering and thereby forming a uniform bondbetween them..

, Among the solvents which havebeen found suitable for the purpose ofsolventsealing may be included alcohols of both the aliphatic and aro-':matic series and containing one or more hydroxyl groups such as methyl,ethyl and normal butyl alcohol, glycerol, benzyl alcohol andcyclohexanol; derivatives of alcohols, such as esters of monoorpolyhydric alcohols,- typical examples of which are ethyl acetate,monacetin and diacetin, respectively; keto alcohols, such as diacetonealcohol; aromatic ketones, such as acetophenone, benzophenone, andcyclohexanone; mixed etheresters of aromatic or aliphatic acids, such asethoxy ethyl phthalate, mixed ether alcohols, such as the monobutylether of ethylene glycol and the monoethyl ether of ethylene glycol;diacyl derivatives of dihydroxy alcohols, such as glycol diacetate;monoacyl derivatives .of the monoalkyl ethers of glycol, such as.derived from the monoethyl ether of ethylene glycol and others. Thediscovery that the abovementioned compounds may be used for this purposeis not to be understood as forming part of our invention, since this isthe invention of C. J. Staud and William O. Kenyon, as set forth intheir Patent No. 1,925,509.

It is to be understood thatthe terms gum and resin are -used herein andin the claims interchangeably and when reference is made to a gum it isto be taken-for the purposes of our invention as also including bothnatural and synthetic materials.

Furthermore, although the specific examples above given are directed to,and the foregoing specification is chiefly concerned with, sheetingcomposed of cellulose acetate, it is to be understood that we are not-tobe limited thereby, as our invention is applicable to thin sheetingcomposed of any cellulosic material to which a gum-wax coating willadhere well; such, for instance, as

cellulose acetate propionate, cellulose acetate butyrate, cellulosepropionate or butyrate, or that cellulosic material which is commonlyknown as Having now particularly described our inven- I tion, what weclaim as new and desire to secure 'by letters Patent of the UnitedStates is:

2,019,048 materialmay be used, depending upon the use to 1. The processof moistureprooflng thin, flexible, transparentcellulose acetatesheeting adapted for wrappingpurposes which comprises first applyingthereto an adhesive layer essentially consisting of gum' and thereaftersu- 5 perimposing on said gum layer a second layer consistingpredominately of wax.

2. The process of moistureproofing thin, fiexible, transparent celluloseacetate sheeting adapted for wrapping purposes which comprises applyinga layer essentially consisting of gum to the sheeting, drying thecoating thus formed, thereafter applying a coating consistingpredominately of wax, and subjecting the double coating thus formed to atemperature 'suillcient v to cause at least partial coalescing of thegum and wax layers.

3. The process of moistureproofing thin, flexible, transparent celluloseacetate sheeting adapted for wrapping purposes which comprises applyingto the sheeting a thin coating essentially consisting of a gum or resinin a molten condition and thereafter superimposing a-coating consistingpredominately of wax on said first coating.

4. The process of moistureproofing thin, flexible, transparent celluloseacetate sheeting adapted for wrapping purposes which comprises applyingto. the sheeting a thin coating of' ester gum in a molten condition,applying sufficient heat to dry the coating thus produced, and applyingon the first coating a second coating of molten paraflin.

5. The process of manufacturing thin cellu lose acetate sheeting of athickness of the order of .001" which comprises first applying to anuntreated cellulose acetate base sheet a solution comprising 1% of estergum dissolved in a solvent consisting of 80% toluene and 20% ethylenedichloride, subjecting the sheet to a temperature of 50-105 C. for alength of time suflicient to evaporate off the solvents and leave a gumcoating closely adhering to said'sheet, and thereafter applying to saidgum coating a solution comprising 1% paraflin dissolved in a petroleumdistillate boiling between 60 and 70 C., and evaporating off thesolvent.

6. The processof moistureproofing thin, flexible, transparent celluloseacetate sheeting adapted for wrapping purposes which comprises firstapplying to the surface of the sheeting a thin coating essentiallyconsisting of gum and thereafter superimposing on said gum coating acoating comprising a mixture of a gum and. wax. I 5.

7. The process of moistureprooilng thin, flexible, transparent celluloseacetate 'sheeting adapted for wrapping purposes which comprises firstapplying to the surface thereof a thin coating essentially consisting ofgum and thereafter superimposing on said gum coating a second coatingcomprising a mixture of a gum and wax in which the wax predominates.

8. An article of manufacture comprising a thin, flexible transparentsheet of cellulose acetate adapted for wrapping purposes of a thicknessof about .001" having closely adhering to the surface thereof a layer ofester gum, said layer having superimposed thereon and adhering theretoan outer layer consisting predominately of paraiiln.

9. An article of manufacture comprising a thin; flexible, transparentsheet of cellulose acetate adapted for wrapping purposes having aclosely adhering coating essentially consisting of a gum, said gumcoating having superimposed thereon and adhering thereto an outercoating consisting predominately of wax.

10. An article of manufacture comprising a I thin, flexible, transparentsheet of cellulose acetate adapted for wrapping purposes having a wthin, closely adhering coating essentially consisting of gum, said gumcoating having superimposed thereon, and adhering thereto, an outersisting of gum, "said gum coating having superimposed thereonandadhering thereto an outer coating comprising a mixture of a gum and awax in which-the wax predominates.

12. The process of 'moistureprooflng sheeting composed oi thin,flexible, transparent cellulosic sheet material adapted for wrappingpurposes which comprises first applying an adhesive layer essentiallyconsisting of gum and'thereaiter superimposing on said gum layer asecond layer consisting predominately of wax.

13. An article of manufacture comprising a thin, flexible,-transparentsheet of cellulosic mathereon and adhering thereto an outer coating 15consisting predominately of wax.

" NORMAN F. BEACH. JAMES G. 'MCNALLY

